Merge branch 'sj/string-list'

Merge branch 'sj/string-list'

The "string-list" API function to find where a given string would
be inserted got updated so that it can use unrealistically huge
array index that would only fit in size_t but not int or ssize_t
to achieve unstated goal.

* sj/string-list:
  refs: enable sign compare warnings check
  string-list: change "string_list_find_insert_index" return type to "size_t"
  string-list: replace negative index encoding with "exact_match" parameter
  string-list: use bool instead of int for "exact_match"